Physics Nuclear Physics MDCAT 2014
PMDC Verified Question 74 of 98
A beta particle is a fast-moving electron. During a \(\beta\) decay how the atomic number and mass number of a nucleus change?
A
Atomic number: Remains the same, Mass number: Increases by one
B
Atomic number: Increases by one, Mass number: Remains the same
C
Atomic number: Increases by one, Mass number: Decreases by two
D
Atomic number: Decreases by two, Mass number: Decreases by four
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Atomic number: Increases by one, Mass number: Remains the same


Concept:

Beta (\(\beta^{-}\)) decay is fundamentally the transformation of a neutron into a proton within the nucleus.

Formula:

$$ _{0}^{1}\text{n} \rightarrow _{1}^{1}\text{p} + _{-1}^{0}\text{e} $$

Solution:

  • Because the nucleus gains one new proton, its Atomic Number (\(Z\)) increases by 1.


  • Because a neutron is simply exchanged for a proton, the total count of nucleons (protons + neutrons) does not change. Thus, the Mass Number (\(A\)) remains the same.


Why other options are incorrect:

Option D perfectly describes alpha decay. Options A and C propose mass changes that violate fundamental nucleon conservation in beta decay.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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